A monolithic broadband 10-50 GHz distributed HEMT mixer including active LO-RF combiner

Abstract

A millimeter-wave GaAs HEMT MMIC distributed mixer covering the RF frequency range from 10 to 50 GHz with IF frequencies from several MHz to 5 GHz was developed. The active devices are AlGaAs-GaAs HEMTs with a gatelength of 0.2 /spl mu/m and a gatewidth of 2/spl times/25 /spl mu/m. The conversion gain of the mixer is better than -3 dB over the frequency range at an LO power of less than 5 dBm without IF amplification. The RF and the LO signals are fed through an active distributed combiner with 2 dB gain and LO to RF port isolation of 20 dB. The size of the single mixer is 1.5/spl times/1 mm/sup 2/ and of the combiner including bias networks is 2/spl times/1 mm/sup 2/. An integrated broadband mixer chip including the LO and RF combiner was fabricated with a size of 4/spl times/1 mm/sup 2/.